What Matters Most
by nonchalantxfeelings
Summary: Elysia, a scientist, offers Erwin the chance of getting back his arm. The catch: he needs to stay alive in order to go through with the operation. Simple, right? But that wasn't really the catch, was it? The real catch for the pair was something more, something that was out of their league and something that couldn't be controlled. So what was it then? ErwinXOC
1. Chapter 1

**Author's Note:** Happy New Year! Hehe, I've been wanting to upload this since my mind came up with this idea. Sadly, my break is going to end soon so I won't be updating until a while... There aren't any spoilers in this story, except for the fact that Erwin loses his arm. Besides that, this story takes place in the anime version. The main pairing of this story is Erwin and OC. I don't know if I'm going to keep Levi's crew alive or not... Anyway, Enjoy!

 **Disclaimer:** I do not own Attack on Titan.

* * *

Chapter One

"And that's it!" Elysia exclaimed.

Levi rolled his eyes. Erwin and he have been stuck here, in a laboratory with no one else but Elysia, head scientist of the place. She was going on about some lab experiment which involved Titans and which could potentially give Erwin back his arm and other soldiers their missing limbs. Levi was disinterested the moment she started talking, but Erwin was captivated by it, even though his facial expression was stoic. Levi regarded the time. It was midnight.

Both of the boys stared at her as she took out some more blueprints from a drawer.

"Look here. This is the part where we have to extract the titan's arm, but we need a way to preserve it since their bodies dissolve when in contact with air after it's been dislocated right? So here," she pointed at another part of the organized blueprint, "is where this," she pointed with her other hand at a design and calculations that Levi couldn't decipher, "comes into play. It serves as a preservation of a titan's body." She smiled at Erwin. "And then you know what comes next. The research, the experiments and -" before she could continue, Levi interrupted her explanation.

"What's the catch?" Levi asked, knowing that Elysia was hiding something about her experiment and it was now or never to figure it out.

"The catch is the Titans." She said vaguely.

"Titans?" Erwin inquired, still having his stoic mask in place.

Elysia nodded. "The test subjects are Titans. I'll be needing a few… samples." She said.

"And where are you going to be getting these Titan samples?" Levi asked.

Elysia head snapped up to meet his eyes. "That's where you come in." She said boldly.

"Me? And what made you think I would help out with your experiment?" He questioned, although he wouldn't hesitate to help his superior. He just wanted to spike her a bit, to see how far she was willing to go to… entertain him.

"Well, wouldn't you want to? You wouldn't be helping only," she motioned to Erwin, "him out. If this is a success, then you'll be helping out with more people." Elysia retorted.

Erwin intervened their conversation "If? So you have doubts in your experiment?" He questioned.

"Look, everyone has their doubts. If they didn't then they aren't human." Before Levi could interrupt her she added, "Captain Levi you're an exception. You're not human." She finished.

Levi smirked. The girl knew how her place, but it wasn't going to stop her from speaking her thoughts.

"You're going to help right?" She asked Levi.

Levi shrugged. "It depends. It's going to be a challenge to get a sample without killing the Titan." He said with a vicious gleam in his eyes, only to have it disappear a second later.

Levi observed Elysia while Erwin was having a look of her other blueprints that she designed. Elysia was hopping around the lab, organizing some products on some shelves. He watched her as she reached for something that was on a shelf that was beyond her level. Erwin peered over to her as well to watch her struggle. Aware of their attention on her, Elysia smiled towards them. Then she jumped and knocked everything that was on the shelf, but got ahold of what she needed.

"Alright." She dusted off the imaginary dust off her coat and walked over to them. She handed them the small bottle that was filled with blue liquid. "This is the thing that will preserve a titan's body until it reaches our refrigerator." She said. "The only problem, is that we need a way to bring the arm here without alarming the citizens." She said.

Both of the boys nodded in understanding. Bringing a part of a titan into Wall Sina was a big deal. Considering that the King lived there and his goal was to prevent any Titan from coming in, this was going to be tricky.

"How long is this going to take?" Levi asked, wanting to know how much of his efforts were going to be wasted.

"As soon as I get the sample I can do some research and then we'll proceed with the process. So I'd estimate about a month after I get the sample." Elysia said.

Erwin nodded. Even though he wanted it to be sooner, her didn't want to risk the outcome of a malfunctioning arm.

"If you have any spare time before your next expedition, it'd be great for you to stop by so I can take some measurements and make some basic calculations on it until the sample arrives." Elysia elaborated.

Erwin nodded in approval. "Expect me sometime this week. It won't be until next week that we'll be leaving for the next mission."

Elysia smiled. "Stay alive by then Commander Erwin." She regarded Levi begrudgingly but still genuinely. "You too Captain Levi."

* * *

Elysia removed her lab coat and hung it on a hook before reaching for her jacket. Ready to leave, the boys gathered their belongings too.

Elysia headed in the opposite direction from them and bid them a farewell.

The walk to their apartment was quiet. Levi regarded Erwin's tense composure. Erwin balled his fists. Levi observed his movements without comments.

"It's going to be beneficial if this is a success." Erwin said, breaking the silence amongst them.

Levi didn't do anything to show that he heard what Erwin had said.

They separated paths and Erwin to his apartment, heading straight to the washroom once he entered his lonely suite and stripped himself of his clothes. He observed his body in the mirror. He was muscularly built, with a tall frame reaching a height of 6,2 which was often advantageous while fighting Titans. He reached for his razor on a higher shelf, remembering how Elysia struggled to reach something on a high shelf and how she didn't ask for help. He started to shave the small amount of hair that collected around his chin area, ready to grow into a beard. He stared into his reflection and into his clear blue eyes to see that it was empty of any emotions. They were dead. He finished shaving and placed it on the high shelf again, ready to shower.

After his shower, and dinner, Erwin headed to bed. He settled himself onto his mattress and stared at the dark ceiling and the small streak of light that escaped from the window. He balled his hand into a fist, gripping the blanket with a thought running through his mind the entire time until he fell asleep. _I'm going to get my arm back._

* * *

 **Author's Note:** So how was it? I know it was short, but I would really appreciate it if you guys left a review telling me what you think. Oh and just a notification: This story, along with all of my other stories, have not been betaed so please let me know if there are any errors or concerns. Check my profile for any updates!

Please review, constructive criticism much appreciated!


	2. Chapter 2

**Disclaimer:** I do not own AOT.

* * *

Chapter Two

"Get out of here, you rat!" A kid was forcefully shoved out from the store. Everyone stared as the dirty boy scurried out, with two loafs of bread in his hands.

"Wait! Get back here! I'll have you arrested!" The shopkeeper ran out of the shop, shouting at the boy.

Everyone kept on staring as the owner stayed where he was, yelling. The boy ran into an alleyway as the shopkeeper muttered some profanities under his breath as he went back into his shop. "Stupid kids."

Elysia headed into the shop and browsed for a while. Everyone in this neighborhood was rich since they were all employed by the king. They were always surprised when they saw someone else from outside the walls. She picked up her daily groceries before heading to the counter to pay for her food.

"That'll be 39.98$." The owner registered her food into bags. Elysia raised one of her eyebrows. "Excuse me?" She asked again. It hadn't been that expensive the time before.

"39.98$," The man repeated. "Someone's gotta pay for that boy." He replied. Greedy man. Elysia didn't complain any further and paid for her groceries along with an added bottle of water. "Have a nice day…" The old grumpy man said. Elysia rolled her eyes before leaving.

She headed to the alley way where she had seen the little boy disappeared to. She knew that it was reckless, he probably ran far away, but it was still worth a shot. As Elysia headed through the dark hall, she clutched her shopping bag and the bottle of water in her other hand.

"Hello?" She called out. There was no reply. "Hello…?" She said, a bit louder than the time before. She stopped, trying hard to listen. She was about to turn and head back, thinking that it was stupid to even try to find the boy until she heard a faint sound.

"…" She stilled in her tracks. What was that sound? She stayed still, waiting for any more sounds. The alley way stayed silent. Elysia crouched down, set the bottled water on the ground and left.

* * *

Even with the earlier incident, she was still early.

"Morning." She said as she entered the building. People bowed in respect as she acknowledged them.

"Miss, you have a visitor at one o'clock this afternoon." A woman with a clipboard approached her. Elysia couldn't remember her name, was it Helen? Or Ellen? Whatever it was, she nodded.

"Who is it?" She asked.

"They wouldn't say. They just say that they wanted to see you." The woman replied. Elysia nodded. "I'll be ready." She wondered who it was. Could it be Erwin? Was he going to be visiting her so soon? Well either way, she had to prepare for the measurements.

Elysia made her way to the laboratory, gathered up a few materials and set them aside in a cart.

"Where are you taking those?" Peter, a coworker asked.

"To the observation room 13." She replied as she hauled the cart out of the room, taking the key to room 13 along with her.

She unlocked the enclosed door and entered the dark room. To her left was the light switch to which she used. The light bulb hanging in the center of the room illuminated the small room in a yellow bright light. Elysia pulled the cart to the side of a wall as she closed the door behind her. She regarded the clock on the wall. She had a few hours until her mysterious visit to prepare.

* * *

"Captain Levi?" Elysia's voice rang out in the empty room.

"Levi." He responded.

"Right…" Elysia said.

The two had a history together. She was a… 'comrade' of his during their training sessions for attacking Titans. It wasn't until she was offered a job at a science community when her relationship with Levi started to grow.

" _You guys aren't serious, are you?" Elysia said to the other two in the room. They stared icily back at her._

" _Well what does it look like to you?" Levi replied. "This isn't a game, Elysia." He said._

 _Elysia clenched her jaw. "I know this isn't a game. That's why you shouldn't be going! You'll… you'll…" She wanted to scream at them some more, but she couldn't find the courage to. They were leading themselves to their own deaths._

" _Elysia…" Hange's voice reached her ears. When she tried hugging her, Elysia took a step back._

" _No." She said. "I… Why would you guys. We don't even know how… And yet, you want to risk your lives? For what?" She knew she sounded weak. The three had been accepted to work together at the King's Palace, yet, the two refused to._

" _Why…?" She said again._

"…" _The room remained silent._

"Elysia? Elysia…?" Levi's voice was slowly calling her back to reality.

"Hmmm?" She hummed, trying to forget the memories.

"I asked you, do you have time?" He asked.

Elysia nodded. "Right this way." She said, leading him to another location even if the whole building was already vacant.

The walk to her lab was silent. Levi watched her stiff posture, no matter how hard she was trying to relax. She had grown, almost past his height even, though he would never admit that aloud.

"So, what are you here for?" Elysia tried to start a conversation.

"…" Levi remained silent.

Elysia stopped in her tracks to look back at him. "…Levi?" She questioned, tilting her head to the side.

Levi avoided her stare as he continued walking. He knew the way to her lab so she didn't have to guide him.

They finally reached the lab where Elysia turned on the lights. "So, what's up?" Elysia tried again, expecting an answer this time."

"I… I –" Levi's answer was cut short.

"ELLL!" A voice was screaming for Elysia before her door was busted open with a panting stranger.

"Peter…?" Elysia' attention was diverted to the young man at the door.

"Want to get lunch together?" He asked. Noticing Levi, his posture straightened. "Captain Levi." He acknowledged his superior.

Levi nodded back.

"Peter, I'm kind of busy right now, but maybe next time?" Elysia replied.

"Oh, sure thing. Sorry for this, I'll be going now." The nervous man raked his fingers through his messy blonde hair before closing the door and heading off.

"Sorry about that, you were saying?" Elysia said.

"It's been 3 years since… since your discovery. And on –" Elysia cut him off.

" _Our_ discovery." She corrected him.

"And on behalf of the Survey Corpse, today we give you our thanks." He saluted her, his hands balled into fists using the usual salute that each soldier learned.

Elysia smiled. "It's been a long time since then."

"Without your advanced research, we would have never found the Titan's weakness." He said.

" _Our_ research, Levi." She said. "Remember? You were the one who was brave enough to execute that silly theory that popped into my head." Elysia approached Levi and stood next to him, looking out the building's windows into the grey and cloudy sky.

"Thanks to you too, Levi." She said.

They shared a moment of peace, reminiscing about the past.

 _Her friends' faces showed a mix of amazement, awe and sadness._

" _Congratulations Elysia!" Hange said._

 _Levi snorted. "Still working for the greedy bastard?" He said._

" _No." There wasn't any hesitation in Elysia's voice._

" _I'll be working to find a way to bring down the Titans and save humanity." She said._

" _What's there to even save?" Levi said._

 _Noticing that a fight was about to erupt, Hange stopped their discussion. "Come on guys, let's try to at least get along." She tried to reason with them."_

 _Elysia wasn't about to step down. "So who are you trying to fight for then? Why are you even joining the Survey Corpse? " She retorted._

" _Don't get me wrong Elysia. I have my reasons for wanting to fight, it's just not as pathetic as yours." He said._

" _Guys… Let's work together now…" Hange tried to step in the fight._

"We grew up so much from then." Elysia noted.

"We found a way to defeat the Titans together." He said.

"Remember the fights we used to have? They used to get so out of hand!" Elysia chuckled.

"But your reason for fighting… Is it still for the same reason?" He questioned.

"I don't know Levi. Sometimes, I don't know what I'm doing, or why I'm even trying to do anything. I keep on thinking that everything will go to waste, you know? But I want to help others still. That's why I need this project to be a success." She said.

"Do you think that after the project's success that you'll have completed your fighting for humanity's sake?" Levi asked.

The room remained silent.

"I don't know." Elysia finally said.

* * *

Her meeting with Levi was refreshing. It was true, they had come up with the theory together and he had been the one to execute it. Together, they found the Titan's weakness. Because of them, hundreds of lives were spared.

"Elysia…?" There was a knock at the door.

"Come on!" She said.

Peter entered the room again.

"Are you busy?" He asked.

"No, what's up Pete?" She asked.

"Well… I just wanted to apologize for earlier. I didn't know that you had a visitor." He said, embarrassed.

"It's alright Peter. It was just an old friend." She said. She didn't notice the way Peter tensed at the word 'friend.'

"Well, um, I should get going. But let me know if you ever need anything, alright?" He said before leaving the room.

"Sure." She replied.

The rest of the day proceeded peacefully. There were no more visits, so that meant that Erwin didn't come today. But she still made sure that she had all of the equipment ready for when he did visit.

She put on her jacket to head home. The sun was starting to set as she left the building. She headed to the kitchen where she prepared a quick and short meal before she took a shower and headed off to bed.

* * *

She dreamt of Titans that night.

"Levi! Levi!" She was calling out. A Titan was nearing him. "Levi!" She was screaming, but her voice stayed silent.

She watched and kept on screaming for him. "LEVI!" Before the Titan closed his hand around Levi's small body, she woke with a startle.

Sweat covered the sheets. Her heart was racing. Elysia buried her head in her hands while her elbows rested on her knees. _It was just a dream…_

But it had felt so real. Why hadn't she tried to save him? Where was his crew?

She needed to breathe. Quickly, she took her jacket and left her apartment.

The streets were quiet, the sun's rays were starting to show and the birds were soaring in the sky. She pulled her jacket closer to her body, shielding herself from the chilly air.

She passed the grocery store from the morning before. Without thinking, she headed for the alleyway. There was light peering through the long narrow space, and there, she found the small boy crouched next to a little girl, with a thin blanket hanging on them. Next to them was one loaf of bread, probably the one he stole the morning before, and there was a bottled water sitting next to them. She crouched down to see their sleeping faces. She sighed, before giving up her jacket and putting it on the two sleeping figures. It was the least she could do. Where were their parents anyway?

"Thanks…" The boy whispered. Elysia's eyes looked to the young boy to see that he was still asleep. He was probably sleep talking. He snuggled against her jacket as his little sister tilted her head to rest more comfortably on the boy's chest.

To Elysia, this was the humanity that she needed to save.

"Elysia-san?" A voice softly called from the end of the alleyway.

Making sure that the sleeping children were still asleep, she headed out into the open space to find a messenger of the King's.

"Good morning." She said.

"Good morning Elysia-san. Are you busy?" He asked.

Elysia blushed. She was still in her pajamas and she probably looked like a mess at the moment.

Realizing the situation, the stranger clarified himself. "I have something to report to you so I headed to your apartment to see that no one was there. I was getting ready to head to your laboratory when I thought I saw you disappearing through the alley way." He said.

"Oh… Elysia's fine, no need for the san part." She said. "What's the news?" She asked.

"Doctor Hange wishes to invite you to her investigation." He said.

"Investigation?" Elysia asked. She shivered as the wind blew.

"She is gathering information on two captured Titans and wishes for you to assist her." He said.

"That's great!" She said. She couldn't stop her excitement from showing. "When do we start?" She asked.

"Today. I'll be guiding you to the site in 2 hours, and you'll be staying at the campus where the investigation is taking place. Pack for 2 days. I'll be picking you up at your apartment." He concluded.

* * *

 **Author's Note:** Hope you guys enjoyed the little interaction between Levi and Elysia. She'll probably be meeting Erwin in the next chapter, but it won't be for a while until we start seeing the chemistry. Sorry for the long update, it probably won't be until a while for the the next chapter, so I apologize in advance for the long waits. Anyway, please leave me review telling me what you thought of this! Constructive criticism much appreciated!


End file.
